1. Field of the Invention
The present invention relates to functional particles and a preparing method thereof, and more particularly relates to a functional particle preparing method in which plasma irradiation intensity and/or the degree of vacuum are changed during plasma irradiation according to the size of each gap between particles to form grafted polymers having uniform graft lengths on the particles, and relates to a functional particle prepared by the functional particle preparing method. Further, the present invention relates to a plasma treatment method in which particles are fixed in a stacked form to which plasma is irradiated for uniform plasma treatment over the entire particles.
2. Description of the Related Art
The inventor of the present application and others suggest a separation membrane formed by plasma graft polymerization carried out on a fine porous membrane so as to substantially fill pores of the fine porous membrane with plasma-grafted polymers and a method for preparing the separation membrane.
For example, in Japanese Patent Laid-Open Publication No. Hei 3-98632 entitled “Separation Membrane and Separation Method”, a separation membrane formed by plasma-graft polymerizing acrylic monomers on a fine porous membrane made of polyethylene of ultrahigh molecular weight having predetermined porosity and predetermined average pores so as to substantially fill pores of the fine porous membrane with acrylic graft polymers is disclosed. In particular, this separation membrane lends itself to application such as a separation membrane for organic solvent mixtures which separates an organic solvent having high compatibility with acrylic polymers from an organic solvent having low compatibility with the acrylic polymers. Here, it should be noted that the “plasma-graft polymerization” refers to a way in which a fine porous membrane is irradiated by plasma in an environment at a predetermined degree of vacuum and then the plasma treated fine porous membrane is soaked in a monomer solution to graft polymerize the monomers.
Further, in Japanese Patent Laid-Open Publication No. Hei 4-334531 entitled “Separation membrane And Method”, a separation membrane prepared by plasma-graft polymerization carried out on a polyethylene fine porous membrane using a plurality of different types of monomers which vary in solubility to substantially fill pores of the fine porous membrane with grafted polymers is disclosed. It is also described that by graft polymerizing a plurality of types of monomers, a mixture consisting of liquids which are of similar solubility can be appropriately separated.
Still further, in Japanese Patent Laid-Open Publication No. Hei 5-31343 entitled “Separation Membrane, Preparing and separation Method of The Same”, a separation membrane prepared by plasma-graft polymerizing nonaqueous monomers on a polyethylene fine porous membrane to substantially fill pores of the fine porous membrane with grafted polymers is disclosed.
In Japanese Patent Laid-Open Publication No. Hei 5-237352 entitled “Separation Membrane And Separation”, a separation membrane prepared by plasma-graft polymerizing acrylic monomers and cross-linked monomers on a polyethylene fine porous membrane to fill pores of the fine porous membrane with acrylic cross-linked graft polymers is disclosed.
Further, in Japanese Patent Laid-Open Publication No. Hei 6-246141 entitled “Separating Membrane, Its Production And Separating Method” a separation membrane prepared by plasma-graft polymerizing acrylate monomers represented by CH2═CHOOR (R is an alkyl group having 10 or greater carbon numbers) on a polyester fine porous membrane to substantially fill pores of the fine porous membrane with grafted polymers of acrylate monomers is disclosed. By using acrylate monomers as a monomer to be filled in the pores, the obtained separation membrane can selectively permeate organic compounds contained in water so as to be separated from the water.
All of the above-described separation membranes and preparing methods provide a separation membrane in which pores of a fine porous membrane are filled with plasma-grafted polymers and a method for preparing the separation membrane. The plasma-grafted polymers filling the pores selectively separate organic compounds in a solution in response to an environment of the solution around the separation membrane.
In the prior art, when a plurality of particles are subjected to plasma irradiation, in order to uniformly apply plasma irradiation on the surfaces of the particles, the particles are placed on a rotating table to which plasma is gradually irradiated.
Accordingly, the technical concept of carrying out one-time plasma irradiation on a large quantity of particles for subsequent graft polymerization of monomers was not suggested in the prior art.
In recent years, there has been a growing interest in drug delivery systems. In particular, refinements are actively introduced into the drug delivery systems to achieve drug delivery which is programmed with respect to the quantity of release or drug delivery which is programmed with respect to the time of release, or to provide an improved drug delivery system in which drugs are distributed to a specific area. In such a drug delivery system, it is to be desired that particles are used to include a drug and the right quantity of the drug is provided to an appropriate area from the particle in response to an environment around the particles.